Discussion on Application of 3S Technologies in Cadastral Surveying and Mapping

Yonghua ZHAO

Abstract In order to explore the application of 3S technologies in modern urban cadastral surveying and mapping, we analyzed the equipment composition of the global positioning system, the advantages of GPS surveying and mapping technology, and the main functions of RS and GIS technologies. GPS technology can improve the accuracy of boundary points of surveying and mapping areas, thereby improving the efficiency of surveying and mapping work and the accuracy of surveying and mapping information; remote sensing surveying and mapping technology has a large observation range and observation space, and RS technology can be used to collect data in remote mountainous areas to reduce the cost of manpower and material resources in surveying and mapping work; and GIS technology provides important data support for land planning and ownership definition. 3S technologies optimize and streamline the surveying and mapping process with their own advantages, making the cadastral surveying and mapping work more scientific and efficient.

Key words Cadastral survey; GPS; RS; GIS; Control survey

Received: March 7, 2021  Accepted: May 10, 2021

Yonghua ZHAO (1969-), male, P. R. China, senior engineer, devoted to research about engineering survey and cadastral survey.

*Corresponding author.

At present, with the improvement of Chinas economic level and the progress of science and technology, the importance of the overall processing of land cadastral information has become more and more prominent. With the increase in the amount of information in the cadastral surveying and mapping work, the difficulty of the work has increased, and many data issues frequently occur in applications and changes, which poses higher requirements and challenges for related staff. 3S technologies include global positioning system (GPS), remote sensing (RS) technology, and geographic information system (GIS). These three modern information processing technologies are mutually infiltrated and developed independently of each other. With their own unique advantages, 3S technologies provide more comprehensive and complete support for related technical work in cadastral surveying and mapping, optimize and streamline surveying and mapping processes, and make relevant surveying and mapping results fully utilized.

3S Technology

GPS

GPS technology is the global positioning system, also known as the global satellite positioning system, and its equipment is composed of three parts: space satellite part, ground monitoring part and user equipment part. The advantages of GPS surveying and mapping technology are summarized below［1-3］.

① Accurate mapping positioning: GPS uses satellite positioning to achieve the unification of the global positioning system, and can monitor and update in real time, with high accuracy; and the operation is very convenient, without the need for visual operation, saving a lot of time and measurement expenses, and improving the efficiency of surveying and mapping. GPS cadastral survey includes the use of GPS surveying and mapping technology to draw cadastral maps, and the use of map grids to measure the area and boundary points of demolition. In the GPS positioning system, there is also hierarchical positioning. According to relevant regulations, the value, utilization and planning of the land can be used to determine the accuracy of the measurement.

② Short surveying time: GPS technology positioning takes a short time, and as long as the real-time dynamic mode is set, surveying and mapping can be completed in a few seconds. Meanwhile, because GPS technology only needs an observation space of 15° or more to complete surveying and mapping, there is no time and space limitation, and the selection of measurement points is more flexible, which is conducive to work at any time, without the constraints of visible observation.

③ High level of automation: The GPS global positioning system is simple to operate and has a high level of automation. By combining with the RTK system to determine the coordinates, the antenna can be automatically observed after leveling and centering. The system realizes the determination of three-dimensional coordinates through automatic data processing, and the acquisition of measurement satellites, observation and tracking can be automatically completed by the machine. When surveying a survey area with a relatively simple topography, it only needs to set up stations once to complete the observation task within a radius of 5 km, which is much higher than the automation level of traditional surveying and mapping.

④ All-weather positioning: GPS satellites have a large number and are evenly distributed, which can ensure that users on the earth can observe 4-6 satellites at any time, and are not affected by any climatic conditions, and can survey and map all-weather without blind spots.

⑤ The application of GPS technology for cadastral surveying and mapping has more extensive adaptability: Since GPS positioning technology requires relatively low visibility conditions between measuring points during the surveying process, and the accuracy of the GPS control network is also less affected by the network structure, the control points can be selected more flexibly in the cadastral surveying and mapping work. Meanwhile, it can also adapt to a variety of terrain environments and weather conditions, and has a wider range of adaptability［4-5］.

RS

Remote sensing technology is mostly used in the detection and data analysis of long-distance objects. This technology can help people collect and process object information without contacting the physical objects. The working principle of remote sensing technology is to use electromagnetic detectors to transmit the detection signals in the form of light, infrared, and microwave through a measurement platform set up in the high altitude or outer space, and then to scan and photograph the overall character and environment of the ground object and complete the processing and analysis of the feedback data through signal sensing. Then through the processing platform, the data is corrected, converted and recognized, so as to obtain the corresponding remote sensing image for people to study and use. The application of remote sensing technology mostly appears in the fields of the study on the real-time or rapid detection of semantic or non-speech information of the target environment, the detection of changes in the surface environment, and the real-time update of GIS data.

GIS

Geographic information system technology processes, stores and manages spatial geographic distribution data, conducts spatial simulation of the data, and presents the obtained data in a three-dimensional composition. The main functions of GIS technology are summarized below.

① Comprehensive analysis and forecasting functions: GIS technology uses the latest geographic information data, and manages these information data through the application of the systems processing and storage functions, so as to provide accurate and reliable data support for the cadastral surveying and mapping work. In addition, GIS technology also has prediction and evaluation functions, which can process some unknown information, then compare the processed results with the actual situation and find out the differences, and then formulate reasonable solutions to reduce loss in cadastral surveying and mapping.

② Spatial information query and analysis: In the application process of GIS technology, a relatively complete database system has been established, which can carry out real-time collection, management and processing of various data information in cadastral surveying and mapping, and the processed information data and pictures will not be significantly different from the original data. And then through spatial transformation, the query, analysis and reset of information data can be realized. It not only improves the efficiency of data processing, but also realizes the conversion with other data information, and enhances the convenience of query and analysis.

③ Storage and data management: There are two main forms of data in geographic information systems: raster data and vector data, which are less difficult to store, and only need to be placed in the corresponding memory. In a geographic information system, the amount of data that needs to be stored is relatively large, and in different forms, such as pictures, videos, and audios. In order to ensure the quality of data storage, the facilities of optical disks and magnetic disks can be used to increase the storage capacity and enhance the accuracy of data.

④ Output function: For geographic information systems, another powerful function is the mapping function, which can automatically generate corresponding graphic images from the information data in the system, and store them in a designated location with output functions.

Application of 3S Technologies in Cadastral Surveying and Mapping

Application of GPS in cadastral surveying and mapping

Cadastral survey by GPS surveying and mapping technology

The specific work of cadastral surveying and mapping by GPS surveying and mapping technology includes: GPS control survey of house demolition and land acquisition survey, GPS analysis and application in cadastral surveying and mapping, GPS measurement of regional boundary point coordinates, and GPS data processing.

The process of cadastral surveying and mapping by GPS surveying and mapping technology: ① An appropriate control network point, which must have a high degree of accuracy and reliability, is chosen as the reference point for GPS measurement; ② a suitable GPS instrument is chosen to determine the range of the rover in the place to be measured, so as to effectively receive the data sent by the reference network; ③ GPS three-dimensional control network points are selected to determine the basic structure of cadastral survey, and the conversion coordinate parameters of GPS measurement network points are calculated according to the coordinates of the control network points; and ④ GPS and RTK system are combined［6-8］. The GPS static measurement method is used to compare the measurement result with the result of the RTK coordinate reference station. As long as the measurement result is controlled within the centimeter level, it is a more accurate measurement.

Data processing mainly includes two aspects: data pre-processing and post-processing. First, in terms of measurement data preprocessing, it is necessary to calculate the vectors of each baseline, and compare the calculated results with the observed data to verify the data of repeat observations of edge and loop closing errors. Such data must be compatible with the accuracy indicators of GPS technical measurement specifications. GPS data preprocessing is the processing and sorting of original monitoring data, and it is an important basis for subsequent data adjustment calculations. In the post-processing of the observation data, the adjustment calculation is mainly based on the preprocessed data results. On the basis of the calculation results, two-dimensional constraint adjustment calculation is carried out according to the requirements of control survey of urban cadastral surveying and mapping.

Application Analysis of GPS Positioning Technology in Cadastral Surveying and Mapping

① Reasonably determining the accuracy of control survey: When applying GPS technology for cadastral surveys, the accuracy of control surveys should first be determined reasonably, which is the core link of data collection. Especially when measuring each characteristic point of land ownership, the density setting of control network points and the selection of measurement accuracy must meet the requirements of measurement. In actual work, the relevant GPS control network, triangulation network, traverse network and edge measurement network should be set according to grading.

② Scientifically deploying cadastral surveying and mapping control network: The main purpose of cadastral surveying and mapping is to manage the land more effectively in order to establish a cadastral database and complete land registration and other related management tasks. Therefore, in actual surveying, the surveying and mapping personnel not only need to set up the plane cadastral control network, but also determine the first-level control of different levels of control network points based on the actual situation of the cadastral surveying and mapping project. When GPS positioning technology is used for cadastral surveying and mapping, datum design is one of the key links. When designing the surveying and mapping datum, the surveying and mapping personnel should comprehensively consider factors such as scale, position and direction, and reasonably set the datum position of the control network. When determining the reference position of the GPS control network, a point in the control network can be selected arbitrarily, and its coordinate value can be fixed. In the datum design, various constraints when selecting values will have a greater impact on the accuracy of surveying and mapping.

③ Scientific selection of control network points and surveying and mapping schemes: When using GPS positioning technology to carry out cadastral surveying and mapping, the requirements for the visibility between survey points are relatively low, and the network structure of the control network can be flexibly selected to make the survey operation more simple and convenient. When selecting surveying points, surveying and mapping personnel should comprehensively consider the correlation factors between positioning and surveying results, fully understand the surrounding environmental conditions and topography of the surveying area, and accurately grasp the actual distribution of surveying points, so that they can select the locations of stations more scientifically and reasonably. In addition, when GPS technology is used for cadastral surveying and mapping, although the requirements for the visibility between the measuring points are relatively low, there are higher requirements for the visibility of the air. Therefore, when choosing the locations of stations, they should be away from the radar, transmitting antennas and TV towers and other equipment as much as possible, so as to avoid affecting the measurement. Meanwhile, it should be avoided to set up measuring points on slopes, which will affect the accuracy of the measurement［9-10］.

Application of RS technology in cadastral surveying and mapping

Compared with traditional field surveying technology, the advantages of RS technology in cadastral surveying and mapping work can be summarized in four aspects. First, the remote sensing surveying and mapping technology has a large observation range and observation space, which breaks the geographical and spatial limits of traditional field surveying work. Second, the remote sensing surveying and mapping technology has a fast information processing speed, which can instantly form a data model for all objects in the measurement space in a dynamic or static state, and has an extremely fast imaging speed. Third, remote sensing technology is not affected by external natural factors and can form extremely high-resolution image data in real time. Fourth, remote sensing technology can be used to collect data in remote mountainous areas, thereby greatly reducing the cost of manpower and material resources in surveying and mapping work.

When remote sensing technology is used in cadastral surveying and mapping work, remote sensing technology mostly appears in the processing of medium or small terrain in the proportion range. An important role of remote sensing technology in cadastral surveying and mapping work is dynamic monitoring, which is mainly used to detect land utilization and related data, and then process the measured data information to obtain more intuitive data information and data models for people to study and analyze. The advantages of remote sensing technology are simple operation, fast imaging, and remote sensing technology is less affected by geographical space.

Yonghua ZHAO. Discussion on Application of 3S Technologies in Cadastral Surveying and Mapping

Application of GIS technology in cadastral surveying and mapping

① Arrangement of field survey records: On the basis of field surveys, with districts and counties as units, an independent and interconnected land use database is established, and at the same time, specific survey records in accordance with corresponding technical requirements and specifications are completed. Combined with the graphic data and form data of the land, the attributes of various real-time data of the land are analyzed. The application of geographic information system can help staff to establish a large-scale relational database, which is a typical application of geographic information system in cadastral surveying and mapping work.

② Application of WEB GIS technology in cadastral surveying and mapping: WEB GIS technology is the most commonly used technology in topographic cadastral surveying. WEB GIS technology is to increase the utilization rate of cadastral space through the application of the Internet, so as to collect more data information and complete the information processing work. Meanwhile, the application of this technology can realize timely update and summary of cadastral information.

③ Application of 3D cadastral information visualization: Through the establishment of the three-dimensional space model, the cadastral data can be analyzed and processed in detail, and reasonable decision-making measures can be formulated in combination with the analysis results to ensure the orderly progress of the cadastral surveying and mapping work. In addition, in the three-dimensional geographic information system, through the application of remote sensing technology, positioning technology, etc., real-time supervision of the cadastral situation is realized, the efficiency of data collection is improved, and the quality of surveying work is guaranteed.

④ Dynamic monitoring of land change information: Due to the movement of the crustal plates, the geological conditions will change to a certain extent, and the corresponding cadastral survey information will also have certain variables. If relevant staff want to grasp the relevant information in time and accurately, it is necessary to carry out cadastral survey work from time to time and do a good job in the collection and arrangement of information and data, so as to enhance the accuracy of the survey data and provide help for the follow-up work. Meanwhile, due to the uncertainty of geological changes, dynamic monitoring needs to be done in order to fully understand the information changes, improve the content of the geographic information system database, and ensure the accuracy and reliability of the data［11］.

⑤ Data storage: Compared with other measurement technologies, geographic information technology has greater advantages in data collection and storage, which can effectively improve space processing efficiency and increase data utilization. Moreover, the geographic information system can carry out scientific and reasonable conversion of data, find out relevant information from it for in-depth research and processing, and timely change and repair the problem information in it, which not only guarantees the accuracy of the data, but also lays a foundation for the improvement of efficiency of the follow-up work.

Conclusions

The application of 3S technologies provides data support and brand-new technical means for modern cadastral surveying and mapping. Using GPS technology to conduct surveying and mapping in house demolition and land acquisition can improve the accuracy of the boundary points of surveying and mapping areas, thereby improving the efficiency of surveying and mapping and the accuracy of surveying and mapping information. Remote sensing surveying and mapping technology has a large observation range and observation space, which breaks the geographical and spatial limits of traditional field surveying work. Remote sensing technology can be used to collect data in remote mountainous areas, which greatly reduces the labor and material costs in surveying and mapping work. The use of GIS technology can obtain accurate geospatial information and provide important basic data for Chinas land planning and ownership investigation. With the continuous development of science and technology, the application of 3S technologies in the future is bound to be more extensive, and the cadastral surveying and mapping work will be more scientific and efficient.

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